CN220894211U - Vortex probe based on eight-shaped excitation - Google Patents
Vortex probe based on eight-shaped excitation Download PDFInfo
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Abstract
The utility model discloses an eddy current probe based on splayed excitation, which comprises a probe shell, and two excitation coils and receiving coils arranged in the shell, wherein the two excitation coils are arranged on the probe shell; the two excitation coils are distributed in an eight shape, and the receiving coil is positioned below the excitation wire. The utility model designs the structure of the vortex probe excited by the splay shape. Firstly, theoretical analysis shows that the influence of direct coupling effect can be reduced due to the structure that the direction of the primary magnetic field generated by the exciting coil is not the sensitive direction of the magnetic field of the receiving coil; meanwhile, the vortex field area in the test piece is mainly positioned below the two feet of the splayed excitation coil, and the area is closer to the receiving coil, so that the detection capability of the probe can be ensured. The probe can detect crack defects under the lifting of 10mm, and has good detection performance on the crack defects. The problem of in prior art when the lift-off is bigger, its detectability is relatively poor is solved.
Description
Technical Field
The utility model belongs to the field of electromagnetic nondestructive detection devices, and particularly relates to an eddy current probe based on splayed excitation.
Background
The eddy current detection is a detection technology based on an electromagnetic induction principle, is sensitive to cracks, inclusions or corrosion defects on the surface and near surfaces, has the advantages of strong universality, high detection efficiency, no need of coupling agents and the like, and has good application prospect.
Eddy current detection techniques have been extensively studied and applied in the detection of metallic materials. In particular, in recent years, with the continuous development of probe manufacturing processes, flexible planar eddy current probes are becoming an important research point for eddy current detection technology. The eddy current probe based on the flexible substrate design can detect the structure with the complex surface, has strong adaptability, and can reduce the influence of lift-off on signals, so that more and more attention is paid.
However, although the flexible coil can improve the detection capability of the probe for defects, the detection capability is generally poor when the lift-off is relatively large due to the weak energy of the flexible coil. How to improve the detection capability of a flexible probe under larger lifting is a problem to be solved practically.
Disclosure of utility model
The utility model aims to provide an eddy current probe based on splayed excitation, which aims to solve the technical problem that the detection capability of a flexible coil is poor when the lifting-off is relatively large due to the fact that the energy of the flexible coil is relatively weak in the prior art.
In order to solve the technical problems, the utility model adopts the following technical scheme:
The eddy current probe based on the splayed excitation comprises a probe shell, and two excitation coils and a receiving coil which are arranged in the shell;
The two excitation coils are distributed in an eight shape, and the receiving coil is positioned below the excitation wire.
By designing the structure of the vortex probe excited in an eight shape. Firstly, theoretical analysis shows that the influence of direct coupling effect can be reduced due to the structure that the direction of the primary magnetic field generated by the exciting coil is not the sensitive direction of the magnetic field of the receiving coil; meanwhile, the vortex field area in the test piece is mainly positioned below the two feet of the splayed excitation coil, and the area is closer to the receiving coil, so that the detection capability of the probe can be ensured.
Further preferably, the two excitation coils are identical in structure and are symmetrically arranged about a vertical plane therebetween.
Further preferably, the upper ends of the two excitation coils are abutted together, and the included angle between the two excitation coils is 15-90 degrees.
Further preferably, the angle between the two excitation coils is 60 °.
Further preferably, the receiving coil is arranged in parallel with the upper surface of the test piece, and the two exciting coils and the side edges of the receiving coil form an isosceles triangle when viewed along the direction parallel to the plane where the exciting coils are located.
A nondestructive testing method of an eddy current probe based on splayed excitation comprises the following steps:
Step 1: building a detection platform: the detection platform comprises a signal generator, a power amplifier, a data acquisition machine card, a signal conditioning circuit, a direct current power supply, a scanning frame, an eddy current probe and a computer; fixing the probe on a bracket, and mounting the bracket and the bracket on a scanning frame; the direct current power supply supplies power to all the partial circuits in a centralized way;
Step 2: the scanning frame drives the bracket and the eddy current probe to integrally move along the surface of the workpiece to be detected, defect detection is carried out, and the lifting distance of the eddy current probe is 0-10mm; the signal generator generates two paths of sine signals, one path of sine signals is transmitted to an excitation coil in the probe after passing through the power amplifier, and the other path of sine signals is transmitted to the phase shifter in the conditioning circuit and is converted into two orthogonal reference signals; the induced voltage signal generated by the receiving coil is processed by the conditioning circuit and then two paths of direct current signals containing characteristic quantity information are output; the acquisition card synchronously acquires data and reads and stores the data through upper computer DAQExpress software in the computer;
Step 3: and analyzing the confirmation of the workpiece according to the detection signal of the eddy current probe.
Further optimizing, the corresponding parameters of the receiving coil and the exciting coil of the eddy current probe are the same, and the parameters are respectively as follows: 30 mm long, 20 mm wide, 0.08 diameter, mm line spacing, 0.18 mm line spacing, two layers and 41 total turns; excitation current frequency was 100kHz
Compared with the prior art, the utility model has the following beneficial effects:
1) The utility model designs the structure of the vortex probe excited by the splay shape. Firstly, theoretical analysis shows that the influence of direct coupling effect can be reduced due to the structure that the direction of the primary magnetic field generated by the exciting coil is not the sensitive direction of the magnetic field of the receiving coil; meanwhile, the vortex field area in the test piece is mainly positioned below the two feet of the splayed excitation coil, and the area is closer to the receiving coil, so that the detection capability of the probe can be ensured.
2) The probe can detect crack defects under the lifting of 10mm, and has good detection performance on the crack defects. The problem of in prior art when the lift-off is bigger, its detectability is relatively poor is solved.
Drawings
FIG. 1 is a schematic diagram of a flexible eddy current probe detection principle;
FIG. 2 is a schematic diagram of a Comsol numerical simulation model according to the present utility model;
FIG. 3 is a diagram of the detection signal of the probe in analog simulation;
FIG. 4 is a schematic diagram of a stent structure;
FIG. 5 is a graph comparing detection signals for different angles of the splayed excitation coil;
FIG. 6 is a graph of signal peaks and peaks at different angles of the excitation coil;
FIG. 7 is a graph of the detection signal of a probe when detecting cracks of different depths;
FIG. 8 is a graph of the detected signal of the probe at various liftoff.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present utility model more apparent, the technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are some embodiments of the present utility model, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
The detection principle of the flexible eddy current probe is the same as that of the conventional eddy current detection, as shown in fig. 1, after a sine alternating current with the frequency f is introduced into an excitation coil, a primary magnetic field with the same frequency is generated in space, and eddy current is induced on the surface of a test piece by the magnetic field; the change of the eddy current on the surface of the test piece can generate a magnetic field with the direction opposite to that of the primary magnetic field, which is called a secondary magnetic field; both the primary magnetic field and the secondary magnetic field generate induced electromotive force at two ends of the induction coil, namely detection signals. It is apparent that the signal U 0 generated by the direct coupling of the primary magnetic field to the receiving coil is independent of the test piece, whereas the signal Δu generated by the coupling of the secondary magnetic field to the receiving coil contains the component defect information and is the signal required for detection. For the flexible eddy current probe, when the structure of the excitation and receiving coils adopts an upper layer and a lower layer parallel design (the receiving coils are shown by red line dashed lines in fig. 1), the direct coupling signal U 0 has larger interference on the detection signal; when the excitation and receiving coils are designed left and right (the receiving coils are shown by blue-line dashed lines in fig. 1), the interference generated by direct coupling is small, but the Δu is small due to the long distance between the receiving coils and the eddy current field area in the test piece, so that the detection capability of the coils is reduced. Therefore, for flexible coils, it is desirable to ensure the detectability of the coil while reducing the direct coupling signal.
In this regard, the present application contemplates a flexible eddy current probe based on "splay" excitation as shown in fig. 2. Comprises a probe shell and two exciting coils 21 and receiving coils 22 arranged in the shell; the two excitation coils 21 have the same structure and are symmetrically arranged about a vertical plane between the two excitation coils, and are distributed in an splayed shape as a whole; the receiving coil 22 is arranged parallel to the surface of the test piece 1 and below the excitation coil, i.e. in the projection area of the excitation coil on the surface of the test piece. The sides of the two excitation coils and the receiving coil form isosceles triangles when viewed in the direction parallel to the plane in which the excitation coils are located.
In the present embodiment, the number of the receiving coils 22 is 1, and an absolute coil is formed. In other embodiments, the number of receiving coils may be 2, and then a differential coil is formed.
In this embodiment, the angle between the two excitation coils is 60 °. In other embodiments, the included angle between the two excitation coils may be any angle in the range of 15 ° to 90 °.
Because the direction of the primary magnetic field generated by the exciting coil is not the sensitive direction of the magnetic field of the receiving coil, the probe structure can reduce the influence of direct coupling action; meanwhile, according to the magnetic field distribution rule, the vortex field area in the test piece is mainly positioned below two feet of the splayed exciting coil, namely the exciting coil is positioned in the projection area of the test piece, and the distance between the area and the receiving coil is relatively short, so that the detection capability of the probe can be ensured.
In order to verify the performance of the flexible eddy current probe excited in an eight-shaped manner, simulation and test are performed respectively.
To further verify the analysis of the detection principle described above, the designed probe is subjected to electromagnetic field frequency domain analysis using an AC/DC module in finite element simulation software COMSOL MultiPhysical, and a geometric model is built, as shown in fig. 2. Wherein the material of the test piece to be tested is carbon steel, and the thickness is 4mm; the length of the crack 4 in the test piece is 15mm, the depth is 2mm, and the width is 0.35mm; the sizes of the single exciting coil and the receiving coil are the same, the length and width of the inner side are 2mm and 1mm mm respectively, and the length and width of the outer side are 6mm and 5mm respectively (the coil size used for simulation is smaller to reduce the calculation amount); the included angle between the two excitation coils is 80 degrees.
The eddy current field in the test piece is mainly concentrated in the projection area of the splayed exciting coil on the surface of the test piece, which is consistent with the theoretical analysis conclusion. In addition, due to the distribution characteristic of the vortex field on the surface of the test piece, when the probe approaches to and departs from the crack, the detection signal is stronger; and when the probe is positioned right above the defect, the detection signal is 0V. Fig. 3 shows a detection signal of the probe, wherein the abscissa corresponding to the wave crest and the wave trough respectively represents the verticality of the probe approaching to and separating from the defect position, and the 0 coordinate represents the position of the probe right above the defect.
1) Building an experiment platform:
To verify the probe performance, an experimental bench was built. The experimental platform mainly comprises a signal generator, a power amplifier, a data acquisition machine card, a signal conditioning circuit, a direct-current power supply, a scanning frame, an eddy current probe, a carbon steel test piece, a computer and the like. The signal generator generates two paths of sine signals, one path of sine signals is transmitted to an excitation coil in the probe after passing through the power amplifier, and the other path of sine signals is transmitted to the phase shifter in the conditioning circuit and is converted into two orthogonal reference signals; the induced voltage signal generated by the receiving coil is processed by the conditioning circuit and then two paths of direct current signals containing characteristic quantity information are output; the acquisition card synchronously acquires data and reads and stores the data through upper computer DAQExpress software in the computer; the direct current power supply supplies power to all the partial circuits in a centralized way. In addition, for the convenience of experiments, a probe support is designed, and the probe 2 is fixed on the support 3. As shown in fig. 4, the stand 3 is mounted on the scanning frame by the clamping assembly 31, and scans the test piece under its clamping. The probe used in the experiment has the same excitation and receiving coils, and the parameters are as follows: 30. 30 mm long, 20. 20 mm wide, 0.08 wire diameter mm wire spacing 0.18 mm wire spacing, two layers, 41 total turns; the excitation current frequency is 100kHz; the test piece is a carbon steel flat plate test piece, and has penetrating crack defects with the width of 0.5mm, the depth of 5mm, the depth of 4mm and the depth of 3 mm.
2) Probe angle optimization:
Considering that changing the angle of the splayed excitation coil influences the coupling of the primary magnetic field and the receiving coil and the coupling of the secondary magnetic field generated by the eddy current field induced by the test piece and the receiving coil, and further influences the detection signal, the included angle of the splayed excitation coil is optimized through experiments. FIG. 5 shows the detection signal of crack defect with the probe scanning over width of 0.5mm and depth of 5mm when the included angle of the splay exciting coil is changed from 15 degrees to 90 degrees. As can be seen from the figure, the eddy current probe detection signals based on the splay excitation are distributed in a sinusoidal shape, and when the probe is positioned in a perfect area, the signal amplitude is almost 0V, which is consistent with the simulation result. Furthermore, it can be seen from the figure that the morphology and signal-to-noise ratio of the signal varies with the angle of the coil. The signal to noise ratio is best when the included angle of the splayed excitation coil is 60 degrees. Further, fig. 6 shows the peak-to-peak value of the signal as a function of the angle of the excitation coil. As can be seen from the figure, the peak-to-peak value of the signal is maximum when the included angle of the "splayed" excitation coil is 60 degrees. Therefore, the performance of the splayed excitation coil is considered to be best when the included angle of the splayed excitation coil is 60 degrees. In the subsequent experiments, excitation coils with an included angle of 60 were selected.
3) Probe performance analysis:
FIG. 7 is a signal of detection when the optimized probe is used to scan sequentially through 5mm, 4mm and 3mm crack defects. The probe can detect all defects and has high signal-to-noise ratio. Meanwhile, the signal peak value and the peak-peak value obviously change along with the depth of the defect, so that the method can be used as the characteristic quantity to quantify the size of the crack defect.
FIG. 8 shows a signal for detecting a crack having a width of 0.5mm and a depth of 5mm when the probe lift-off is changed from 0 to 10 mm. As can be seen from the figure, although the peak value and peak-to-peak value of the signal decrease with increasing lift-off, when the lift-off is 10mm, the probe can still detect crack defects with a width of 0.5mm and a depth of 5mm, and the signal-to-noise ratio of the signal is high. It can be proved that the probe has good detection performance under the condition of large lifting.
In conclusion, according to the eddy current probe based on the splayed excitation, the direction of a primary magnetic field generated by the excitation coil is not the sensitive direction of a magnetic field of the receiving coil, so that the structure can reduce the influence of direct coupling action; meanwhile, the vortex field area in the test piece is mainly positioned below the two feet of the splayed excitation coil, and the area is closer to the receiving coil, so that the detection capability of the probe can be ensured. And secondly, carrying out optimal design and performance analysis on the probe through experiments. The experimental results show that: when the included angle of the two excitation coils is 60 degrees, the detection capability of the two excitation coils on the carbon steel test piece used in the process is strongest; meanwhile, the designed probe can distinguish crack defects with different depths, and can detect crack defects with the width of 0.5mm and the depth of 5mm under the lifting of 10 mm. It can be proved that the probe has good detection performance on crack defects.
With the above-described preferred embodiments according to the present utility model as an illustration, the above-described descriptions can be used by persons skilled in the relevant art to make various changes and modifications without departing from the scope of the technical idea of the present utility model. The technical scope of the present utility model is not limited to the description, but must be determined according to the scope of claims.
Claims (5)
1. The eddy current probe based on the splayed excitation is characterized by comprising a probe shell, a receiving coil and two excitation coils, wherein the receiving coil and the two excitation coils are arranged in the shell;
The two excitation coils are distributed in an eight shape, and the receiving coil is positioned below the excitation wire; the two exciting coils have the same structure and are symmetrically arranged about a vertical plane therebetween.
2. The eddy current probe based on the splayed excitation according to claim 1, wherein the upper ends of the two excitation coils are abutted together, and an included angle between the two excitation coils is 15-90 degrees.
3. An eddy current probe based on "splay" excitation according to claim 2, characterized in that the angle between the two excitation coils is 60 °.
4. An eddy current probe based on "splay" excitation according to any one of claims 1-3, wherein the receiving coil is arranged parallel to the upper surface of the test piece and is located in the projection area of the excitation coil on the surface of the test piece; the sides of the two excitation coils and the receiving coil form isosceles triangles when viewed in the direction parallel to the plane in which the excitation coils are located.
5. The "splayed excitation-based eddy current probe according to claim 4, wherein the number of the receiving coils is 1 or 2.
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| CN202322575813.0U CN220894211U (en) | 2023-09-22 | 2023-09-22 | Vortex probe based on eight-shaped excitation |
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| CN202322575813.0U CN220894211U (en) | 2023-09-22 | 2023-09-22 | Vortex probe based on eight-shaped excitation |
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